Unexpected Electron Transport Suppression in a Heterostructured Graphene-MoS₂ Multiple Field-Effect Transistor...

We demonstrate a graphene-MoS₂ architecture integrating multiple field-effect transistors (FETs), and we independently probe and correlate the conducting properties of van der Waals coupled graphene-MoS₂ contacts with those of the MoS₂ channels. Devices are fabricated starting from high-quality single-crystal monolayers grown by chemical vapor deposition. The heterojunction was investigated by scanning Raman and photoluminescence spectroscopies. Moreover, transconductance curves of MoS₂ are compared with the current-voltage characteristics of graphene contact stripes, revealing a significant suppression of transport on the n-side of the transconductance curve. On the basis of ab initio modeling, the effect is understood in terms of trapping by sulfur vacancies, which counterintuitively depends on the field effect, even though the graphene contact layer is positioned between the backgate and the MoS₂ channel.